William l



Reissued Mar. 18. 1924.

UNITED STATES WILLIAI L. RANK, 0-! PITTSBURGH, PENNSYLVAIIIA.

ABBASIVE FOR GRINDING SMOOTHIKG GLASS.

No Drawing.

Original No. 1,387,649, dated Auguii 16, 1921, Serial Ho. 369,085, filed Ketch 556, 1920.

Application for reissue filed July 8, 1923. erlal En. $58-$81.

1' '0 oil whom it may concern:

Be it known that I, WxLuAM L. Kenn, of Pittsburgh, Allegheny County, Pennsylvania, have invented a new and useful Improvement in Abrasives for Grindin and Smoothing Glass, of which the follow ng is a full, clear, and exact description.

Heretofore, glass, such as plate glass, has been ground and smoothed by the use of send as an abrasive, particularly for the rough grinding. Emery has been used for the final smoothing operation, preliminary to polishing. Coerser grades of sand are used for rough grinding and finer redes for successively finer grinding, inc uding part of the smoothing.

In practice, send for grinding plate glass is generally taken as it comes up from the quarries. if in rock or stone form, crushed, and perlmps Washed (if it should contain much foreign or impure matter), then dried and used; no attmnpt being made to rude or size it or seinerfor uniform her ness. Theretln-e, the bulk remaining will always contain yer cent of fines, of varying degrees of hardness, that are not useful for eonrse grinding, which impedes the operation, or preventing the coarse grains from fully asserting themselves, as the facing or course grinding advances and progresses to o. uniform surfeee.

Therefore. it is obvious that this operation send, which is fed to the grindln Inwehiue, Wasted, more or less, as it is t rown oti" by the centrifugal force of the machine, resulting in waste. Again, as the facing operation progresses, the sand being of varying degrees of hardness and because of its ehareeteristifis. breaks down irregularly, thereby produoin at non-imiform face on the glass termed in t is art bad smooth,

rerpiiring more materiel to work it 0ut, be-

cruise if the smoothing operation is not r- .fect, it produces in the final result ad finish, termed in the art short finish, necessitating that the Work be done over. This short finish may not be discovered until the glass has been polished, which i would require the glass to be sent back to the grinding machine to correct this had work in the grinding and smoothin operation, and of course, necessitates t at the polishing be done over. All this results in loss of time, labor, motive power, reduced production from the machines, exoess of sands and emery, polishing material and obviously increased cost.

I have discovered that oertain crystalline shresire minerals possess charaetoristirs rendering them peculiar-l -e.pplicable for the grinding and smoot ing of plate end other glass. By using thorn, I do away with the use of emery in the final smoothing and use the same material toroughout gli the rinding and smoothing operetimis, no to t 19 polishin operation. The natural mineral which I eve found best suited for this purpose is crysteliine et occurs both in massive d ehnendite, and also in rm. The crystalline form is sineo oystels when woken down to smeiler particles will retain sharp edges of crystalline form. In other words, the larger crystals are made up of smaller crystals which retain their originel crystalline characteristics. Therefore, when the prepared ernet materiel, crushed, sized and freed 'rom its impurities, is applied to the rough grinding operation, properly graded and of uniform i'ierdness and free from any foreign matter, to Whatever extent it is broken down into smelter grains durin this operation, that extent material 1s provided whieh is suitable and advantageous for the succeeding finer grinding and smoothing operations or steps. In practice, I prefer to feed just enough of the posrse garnet materiel in a single batch' to oneflfliii table to carry out the rough grinding opertion, the next grade of the used material which has been graded in the interim durneturel :1 for grinding and smoothing,

ing the rough grinding is fed on the table 05 and the operation cont'nued in the next step; and so on, through the successive gredings of finer materials. i

In the use of sand, after rough grinding, the table and cutters are carefully washed ation thereon. At the end of this opera-{3 to remove all rough sand preliminary to applying the next grade of line sand, be cause any rough sand left will scratch the glass in the next or smoothing operation. In the case of this new material, however, I do not need to wash oil the table between successive steps cl grinding and smoothing. J considerable saving is thus t ller-ted. This i due partly to thc much greater and uniform hardness of the garnet imitcrinl which brd ks down uniformly as emnpared to st; and also to its characteristi s of breaking o'wn in operation. The scalc of hardness in garnet, is about eight, while sand is rated at about live to six.

The grinding opt-ration is out, step by step, without any Washing oil and with the suc ESSlVU grades formed during the successive steps of the operation. The smoothing may then be can rled to Completion by the liner grades of garnet material from the previous later steps of grinding. That is, the material broken up in the grindin steps; is vollcct ed and graded and used tor smoothing. This grading will preferably be ellected automatically by any of the well known gradin systems.

do preparing this material as mined, the crystal form of garnet ore is crushed, the best ore selected, Lhcn furiln-r reduced by crushing, and then inrnred from the gangue or impurities in which it is tlllllltillfid, then further reduced in size and graded into usable or marketable sizes. These operations may be carried on by any well known methods, The crystalline form of garnet contains a very much larger percentage of usable abrasive material, besides which the natural fine sizes made in the grading are crystalline in form, and not fractures, splintens, or flakes; furthermore, the final sizes of the broken up crystals can be used down to the very finest sizes to replace emery, heretofore used in SIl'lOOblllng. These finished sizes can be used down to Hour or dust.

This material may be used to especially good advantage for the grinding and smoothing and finishing of optical glass in which art, the requirement calls, for great. precision), both on account ot' its sharp cutting and lasting properties, and particularly, on account of its peculiar clnirccteristics in reducing itself down in work in successively fine sizes or crystals of thcsnine character.

The material is so hardconipnred to sand that it may be necessary to add to the re coveries from one step liner material for the. next step; and on the other hand, the material recovered from one step may be in excess of that rcquinrd for the next step. In such cases, liner nni'lcr cl may be added beyond that rccmcrcd lion? the previous step or steps, or excess material from any Stepmay be stored.

thus carried intermediate I claim:

1. The method of grinding. smoothing and finishing glass prepni slurry to polishing, comprising supplying to the glass u not nr=il crystalline zibrnsirr of such t'lIL'tlZlLl-l [lint as it is crushed and blohcn the snlrillcr uius or particles thereby Pl'tltltlt'tti 1m: ol' di t inct crystalline form, and ccnt'mmnsly roller-1- ing and supplying to the gl 5 such abrasive during the grinding, smoothing and liuishing operations, substantially as described.

he method of grinding, smoothing and finishing glass preparatory to polishing, comprising supplying to the glass it natural crystalline abrasive of uniform hardness greater than the hardness of sand and of such character that it is. crushed and broken the smaller grains or particles thereby produced are of distinct crystalline form, and continuously Collecting and siqiplying such abrasive in successively finer grades to the glass during the grinding, smoothing and finishing operations in :1 series. of sec ccssivc stages whereby washing of the up; lratus between sun-cssive ra if material Supplied tin-11 n is obviated, substantially as described.

3. The herein described method of grinding and smoothing glass, which consists in fee-din thereto for the rough grinding a natura crystalline abrasive which has been crushed, sized and freed from its impurities and which is of such character that. as it is crushed and broken the smaller grains or particles thereby produced are of distinct crystalline form, collecting and rc-supplyiug to the glass such material in successively liner grades during the various stages of the rough grinding and of the sinootlnng operations until the surface of the glass has been ground and smoothed to e condition in which it is ready for the final polishing, substantiall y as described.

l. The method of surfacing glass to produce the maximum abrasive efl'ect of the abrasive and rubbers,- comprising supplying to the glass ,0. liquid, together with n natural crystalline flibrasivc freed from its gang-no and adapted during the ubrading open-loll, to break down into distinct crystalline form having abrading characteristics similar to the characteristics of the originally supplied abrasive, to thereby maintain between the rubbers and the glass surface being abraded, a. bod of effective abrasive material hereby re ative movement between the rubbers and the glass will insure the continuous abrading of the glass through the medium of the abrasive material and thereby produce uniform abraded surfaces. and not idle reletlve movement of the glass and rubbers caused by non-distinctirc abrasive particles between the rubbers and glass, substantially as described.

j. The method of producing and applyin?) an abrasive for surfacing glass havin to remove foreign matter from the crushed su stantielly uniform hardness and whie crystals, and then using the graded crystals will break down into distinct crystalline to ether with a liquid for surfacing glass, 10 form of smaller size having the same hards11 stantially as described.

ness and other abrading characteristics, In testimony whereof, I have hereunto set; comprising crushing crystalline garnet, my hand.

cleaning and grading the crushed material WILLIAM L. KA'NN.

Certificate qf Correction.

It is hereby certified that in Reissue llctvl'm's Palvnt N0. 15.?96. granted March 18, 1924, upon the application of William L. Kuhn. uf Pittslmrg'h, lelmgvlvanis fur an impl'm-emenc in Abrasives 'for (lrrimlin; am] fimnnthin; Glass, an errm Ap- Fenrs in th printed specifivatinn rcquirin; um'rvl'thm m follows: Page 1. lim l 01' tho won! matters read gut/em; and that the Sllll Letters Pall-ht shnnhl hh Pearl with (ll'lh' correction therein that the .szummay (:onl'mm Ln lh(- nwwi l :hv case in lhv lzltont ()lfice.

Signed and scaled this 6th day of May, A. l). 1921.

lsmLl KARL [PEN NI N Acting /01?!,/e ::'R-$/,m'/ lfl/m/Q 

